4D compressor failure
I am looking to start a discussion on possible causes for a comp failure.
This job is a nightmare. I will be going there Monday to resolve issue and I am just looking to spitball some ideas. Unfortunately for me I have limited involvment on this job and much of the info I have is hear-say from other mechanics.
3 comp rack system, R22 system, ICP style CPC controller that is only being used to monitor and cycle compressors and unloders. 3 ckt's being temp controlled with LL solenoid valves. High temp system 68 degree set point. Defrost is probably electric but have not had enough time on equipment to say for sure, defrost settings are also unknown at this point. Acct is a tomatoe packing plant and refrigeration ckts are not in constant use. Often 1 or more boxes are empty and those sys's are left in a pumped down state. Oil system is using temprite, check valve (differental needs to be checked), oil resivior level unknown, comp's are hooked up with oil equalizing line.
The original call was for 2 compressors offline. 1st comp held off at oil safety (Penn Mechanical). Cleaned P/U tube and started up fine 20 psig differental. 1/2 glass of oil at pot. Oil lil foamy might have liquid refrigerant laying in oil?
2nd comp had thrown rod. This compressor was replaced but contactors were not. Contactors are pitted but are worn. Obviously they should of been replaced (6 wire 2 contactor wiring configuration) Amp draw was aprox 35 amps on each leg at start up under full load, RLA is 60 amps.
New comp ran 1 week and then shorted to ground. 1st compressor off on tripped oil safety. Oil dark but not gritty in rack. Pulled P/U tube and inspected (clean) also keeping 20psig crankcase differental. Oil safety bad and will replace on Monday. Also found and replaced failed phase monitor.
Tech dispatched to site next morning observed heavy sweatback on 3rd comp (possibly flooding back?). New comp sat overnight calling but held out by open in control circuit. Determined to be held off at control module in peckerhead. Line voltage feeding comp was removed, control mod jumped, contactor pulled in. Shut down circuit, put line voltage back, restarted, never observed comp run, Comp had 2 legs shorted to ground, did not check windings prior to starting, possible it was shorted out of the box???
Also CPC board had intermittent supply power problem. Loose wires seemed to be culprit and has been resolved.
So thats what I am up against
Heres my Monday morning game plan:
1. change out comp again
2. check SH @ txv's and @ comp's
3. check LL soleinoid valves for bleed-by
4. acid test
5. considering oil viscosity test
6. if acid change out cores on LL and also put in suctionm cores for clean up.
My thought is that because this rack keeps such a high temp setpoint that the sweating my be indicating a fllodback issue. Foam in oil may indicate liquid in oil. Flooded start conditions may be cause of problem along with bearings being washed out.
I got myself a full plate on Monday and any thoughts or ideas anyone has would be welcomed. Sorry for the lack of specifics on equipment data I will have that stuff once I get onsite.
If you are only reading 20 psi diff oil on the compressors and they are not being flooded out at the time, you better tell the customer to start saving for new pumps in the near future.
I am more concerned with why I have lost that other comp 3 times in two weeks. Any thoughts on that?
Originally Posted by mspanky
Floodback would be my first guess.
Get out a milk crate and babysit this beast.
Monitor EVERYTHING for 24 hours minimum.
Replace those contactors and that pump with 20# oil is crap, too. Copelands want 50# and anything under about 30 is trouble.
If you're gonna sit and watch it for 24 hours. I suggest something a little more comfortable than a milk crate.
Install a rmcc there a dime a dozen now. and install a 16 ai board and temp sensors to monitor temps on systems and oil temp ect.I'll bet your dealing with flood back with that old Ipc as they did not have any drip time. You could install a time delay on each system for a drip time.
Originally Posted by crackertech
Yeah I would love to convert it to an RMCC and take more control over the rack but its doubtfull that I can convince the customer of that.
Im not sure how defrost is set up on this rack. Its possible that its just an off-time set up. The coldest setpoint is only 65. How would adding a drip time help? I doubt its hot gas but I will be checking it out monday to know for sure.
when you're checking your superheats for flood back. Make sure to do it out of defrost too.
My Spidey sense is telling me that your flooding back pretty hard after a defrost cycle.
Yup I have that suspiscion too, as a very real possibility. It would explain the bearings being washed out.
Originally Posted by Phase Loss
Hey, nobody said market work was easy....
Originally Posted by Phase Loss
65 for the LOWEST setpoint?
Are we talking AC, here?